When people know that light has speed and can spread, they begin to explore the essence of light tirelessly.
Newton's Oracle?
At that time, there were two completely different views on what light was.
One is represented by Sir Newton, the man of God in science and the founder of physics? Particle theory? It is considered that light is a particle, that is to say, a beam of light is actually composed of countless particularly small particles, and beams of different colors are composed of different particles.
One was put forward by Hooke and inherited by Huygens? Wave theory? In other words, light is a kind of wave, just like the ripples on the water, which spreads in space in the form of waves.
At that time, both theories could perfectly explain the phenomenon of direct light and refraction, and the two viewpoints collided fiercely. But this balance was unbalanced from the beginning. You know, Newton at that time not only discovered gravity, put forward three laws and laid the foundation of mechanics, but also was the chairman of the Royal Society of England, with unparalleled influence and a large number of people? Lick the dog? What's his opinion? Oracle Bone Inscriptions? It is widely sought after by most people. So for a long time, academia has been? Particle theory? Ruled by ...
However, science will always be a discipline that pursues truth and will never yield to any dignitaries and forces.
Particle theory? Soon challenged by a British doctor who loves acrobatics, Thomas Young designed the famous double-slit interference experiment. In fact, the principle of this experiment is very simple. If we see two mosquitoes flying in the air, their trajectories will not affect each other when they intersect. And if we throw two stones into the water, when the ripples they produce are close to each other, they will interfere. Thomas Young set up two screens. The first screen has two parallel slits from which light shines on the second detection screen. If the light is a particle, two patterns corresponding to the slit size should be observed on the detection screen. But in fact, a series of patterns with bright stripes and dark stripes are displayed on the detection screen.
This proves that only? Interference? Yes, it also proves that light is actually a wave.
Later, scientists passed? Poisson highlights? That is, the diffraction phenomenon of light once again proves the fluctuation of light. At this point, particle theory has temporarily withdrawn from people's sight.
But the bigger problem is coming. According to the classical mechanics theory, the propagation of matter needs medium. For example, sound waves travel by air or other entities. Air is everywhere, so we can hear different sounds anytime and anywhere. Here, the girl also came to break a common sense misunderstanding. Unlike science fiction, which has all kinds of passionate special effects sounds, the real space is actually silent, because in a vacuum environment, sound can't find a way to spread.
So, light, this magical wave, is spread by what? At that time, the scientific community agreed that this thing was: ether.
Ether? And the principle that the speed of light is constant.
If you want to count the most romantic and mysterious existence in the history of science, then? Ether? Must be ranked first, which is the combination of myth and science, aesthetic feeling and rationality. It was first born in ancient Greece and put forward by the philosopher Aristotle. Ether is considered as a material element. The world is made up of water, fire, air and earth, and there is another substance that lives in the upper layer of the sky: ether.
Ether is everywhere, all-encompassing, full of space, and it is a beautiful creation.
When the scientific community finally discovered the wave characteristics of light, everyone began to look for the propagation medium of light: a ubiquitous, imperceptible and eternal substance in space, which is ether! At this point, ether has become the darling of physics.
However, facts prove once again that science will not bow to anyone except truth.
Due to the mysterious nature of ether, proving its existence has become the goal pursued by many scientists, and Michael Sun and Morey are two of them.
They put forward an interesting hypothesis, if the propagation medium of light is ether, and ether fills the whole universe, then when the earth revolves around the sun at a speed of 30 kilometers per second, it will inevitably encounter 30 kilometers per second? Ether wind? Blowing head-on. Then the speed of light will also change because of the direction of the earth's movement, just as people can feel the wind when running in a windless environment, and when we run with the wind, the wind and the crosswind, our bodies will feel very different. So the two scientists designed a clever experiment. They emit two beams of light perpendicular to each other and return to the light source through the lens. According to the ether theory, the propagation speed of these two beams of light should be different. If one beam of light moves in the direction of the earth, then the other beam must be caused by the movement of the earth? Ether wind? It's 90 degrees, which means that one beam of light travels with the wind and the other beam travels with the crosswind. The speed of these two kinds of light must be different.
But the experimental results are simple and full of beauty, but there is no result.
No matter whether it is vertical, intersecting or oblique, no matter how precise the measuring instrument is and how rigorous the experiment is, the result is the same, and the speed of light remains unchanged!
The principle of the constant speed of light shocked the academic circles and directly proved that the ether did not exist, which made? Light? More mysteriously, it is a wave, and the ether does not exist, so how does it spread?
Electromagnetism? Clash of the titans?
While testing the ether crazily here, the field of electromagnetism has been reported frequently.
Since 18 19, the physicist Oster inadvertently found that the small magnetic needle next to the electrified wire would deflect, and scientists began to understand the electromagnetic force gradually. Soon, the electromagnetic field ushered in two geniuses, one is Faraday, the experimental master, and the other is Maxwell, the god of formulas.
First of all, Faraday broke people's obsession with Newton's classical mechanics and discovered the law of electromagnetic induction. I believe that when we were in physics class, we were all? Force analysis? Tortured by this big boss, the physics teacher earnestly stressed that the direction is the opposite, the opposite, the opposite, but I am still young and ignorant, and I will still make mistakes ... but? And vice versa? These two words perfectly embody the characteristics of classical mechanics, and the directions of force and force are always opposite. But the electromagnetic force is different. Faraday found that the force generated by the current on the magnet is not along the connection direction between the wire and the magnetic needle, but perpendicular to this direction, which makes people start to think that maybe Newtonian mechanics does not represent all this. More importantly, in 1846, Faraday found that the polarization plane of light would deflect in the magnetic field. In short, light seems to have an inexplicable relationship with electromagnetism.
However, Faraday dropped out of school in his early years. Although he was good at doing experiments, his theoretical knowledge was still not as good as others, and he could not derive theoretical equations.
His student Maxwell took the torch from the teacher.
19, Maxwell deduced the legendary Maxwell equations and deduced? Electromagnetic waves? The existence of, and boldly guess that light is an electromagnetic wave. 1888, another important task of electromagnetism, hertz verified Maxwell's theory in the laboratory, proving that light is actually an electromagnetic wave, and the propagation of electromagnetic waves does not need any medium.
The Duality and Relativity of Light
Do you think the story is over here? No, it's naive.
Truth is never absolute, and people's exploration of truth never stops.
While Hertz proved that light is electromagnetic wave, he also found that light is particle.
When light shines on different metal surfaces, different reactions will be found, and there was no answer at that time. Finally, Einstein, the man of God who solved all these disputes, stepped onto the stage.
1905, called this year? Einstein miracle year? This year, he published five papers in succession, one put forward the theory of relativity, one laid the foundation of nuclear weapons, that is, E = MC 2, two discussed atomism and Brownian motion, and the last one, which won him the Nobel Prize, was to discuss: photoelectric effect, that is, light has the characteristics of particles and light waves, so light has? Wave-particle duality